Find cos2A if sinA=1/4. and 0<=A<=pi/2?

Question

show work thanks im having trouble

Answer 1

cos2A = cos^2A - sinA

cos2A = 2cos^2A - 1

cos2A = 1 - 2sin^2A

You can use any of the above equasion to solve this kind of problem. I would use the last one because it is the only one that doesn&#039;t have a cosine in it.

cos2A = 1 - 2(1/4)^2

cos2A = 1 - 2(1/16)

cos2A = 1 - 1/8

cos2A = 7/8